非表示:
キーワード:
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要旨:
The fate of plastic debris entering the oceans is largely unconstrained.
Currently, intensified research is devoted to the abiotic and microbial
degradation of plastic floating near the ocean surface for an extended
period of time. In contrast, the impacts of environmental conditions in
the deep sea on polymer properties and rigidity are virtually unknown.
Here, we present unique results of plastic items identified to have been
introduced into deep-sea sediments at a water depth of 4150m in the
eastern equatorial Pacific Ocean more than two decades ago. The results,
including optical, spectroscopic, physical and microbial analyses,
clearly demonstrate that the bulk polymer materials show no apparent
sign of physical or chemical degradation. Solely the polymer surface
layers showed reduced hydrophobicity, presumably caused by microbial
colonization. The bacterial community present on the plastic items
differed significantly (p<0.1%) from those of the adjacent natural
environment by a dominant presence of groups requiring steep redox
gradients (Mesorhizobium, Sulfurimonas) and a remarkable decrease in
diversity. The establishment of chemical gradients across the polymer
surfaces presumably caused these conditions. Our findings suggest that
plastic is stable over extended times under deep-sea conditions and that
prolonged deposition of polymer items at the seafloor may induce local
oxygen depletion at the sediment-water interface.
